Masitinib is a c-kit inhibitor for the potential treatment of cancer (gastrointestinal stromal tumor (GIST), pancreatic cancer, multiple myeloma (MM), metastatic melanoma), inflammatory diseases (mastocytosis, rheumatoid arthritis (RA) and asthma), and CNS disorders (Alzheimer's disease (AD), multiple sclerosis (MS)) in human subjects. It is already approved as a veterinary medicine for the treatment of mast cell tumors. Masitinib is disclosed in WO 2004/014903 A2.
WO 2008/098949 A1 discloses a crystalline form of Masitinib mesylate, hereinafter called crystal form I, characterized by an X-ray diffraction pattern. The positions of the XPRD peaks are disclosed on page 23. It is also disclosed that the form remains dry at 80% relative humidity and thermodynamically stable at temperatures below 200° C.
In the file history of European patent application 11170200.7, applicant's response to the eESR dated Mar. 20, 2012, (hereinunder called “response to the eESR”), two more polymorphic forms of masitinib mesylate are mentioned and named DRX2 and DRX3. DRX2 is described to be a likely hemihydrate which is stable only at 25° C. and which slowly, but fully, converts to DRX1, the polymorph disclosed in WO2008/098949, upon temperature increase. The conversion is described to be even faster in conditions that lower the activation energy barrier. DRX3 is described as an anhydrous form, which is stable under dry conditions only and which otherwise quickly converts to DRX2. It is concluded that DRX1 be the “ideal” candidate for developing a pharmaceutical dosage form, even though it is recognized that DRX1 is mildly hygroscopic.
As DRX1 presently appears to be the only available polymorph suitable for pharmaceutical development, there remains thus a need for a further polymorph of masitinib mesylate suitable for the development of pharmaceutical dosage forms, preferably one with improved properties. Moreover, as hygroscopic solid forms pose a limitation to the types of pharmaceutical dosage forms which can be prepared from them, for the types of excipients which can be used in combination with them and for the conditions and processes, which can be employed during the preparation of a pharmaceutical dosage form comprising a hygroscopic solid form of masitinib mesylate, there is thus a need for a solid form of masitinib mesylate, which is non-hygroscopic at a range of relative humidity which is typical of the regular working conditions encountered during finished dosage form preparation, and which is stable also at temperatures above 25° C.